Circuits and methods for battery charging

1. A battery charging circuit comprising:

a power converter operable for providing a charging power to a battery pack;

a charging control switch coupled to said battery pack and operable for transferring said charging power to said battery pack; and

a charger controller coupled to said charging control switch and said power converter, wherein said charger controller comprises:

a comparator operable for comparing a battery voltage of said battery pack with a first predetermined battery voltage;

a selector coupled to said comparator and operable for selecting a signal from a first signal and a second signal to control said charging control switch according to an output of said comparator; and

a multiplier operable for multiplying a third signal representative of a cell number of said battery pack by a fourth signal representative of a predetermined maximum cell voltage of said battery pack,

wherein said first predetermined battery voltage is a portion of a product of said third signal and said fourth signal,

wherein said first signal is operable for controlling an output of said power converter.

2. The battery charging circuit of claim 1 , wherein said selector selects said first signal when said battery voltage is less than said first predetermined battery voltage.

3. The battery charging circuit of claim 1 , wherein said selector selects said second signal when said battery voltage is greater than said first predetermined battery voltage, and wherein said second signal comprises a pulse signal.

4. The battery charging circuit of claim 1 , wherein said charger controller further comprises a first error amplifier operable for comparing a charging current of said battery pack to a predetermined charging current, and wherein said first signal is generated according to an output of said first error amplifier when said battery voltage is less than a second predetermined battery voltage.

5. The battery charging circuit of claim 4 , wherein said predetermined charging current comprises a predetermined pre-conditioning charging current when said battery voltage is less than said first predetermined battery voltage.

6. The battery charging circuit of claim 4 , wherein said predetermined charging current comprises a predetermined maximum charging current when said battery voltage is greater than said first predetermined battery voltage.

7. The battery charging circuit of claim 4 , wherein said charger controller further comprises a second error amplifier operable for comparing said output of said power converter to said second predetermined battery voltage, and wherein said first signal is generated according to an output of said second error amplifier when said battery voltage reaches said second predetermined battery voltage.

8. The battery charging circuit of claim 1 , wherein said first signal controls said output of said power converter to a third predetermined battery voltage when said battery voltage is less than said first predetermined battery voltage.

9. The battery charging circuit of claim 1 , wherein said first signal controls said output of said power converter to a third predetermined battery voltage when an abnormal condition occurs in said battery pack.

10. The battery charging circuit of claim 1 , wherein said first signal controls said output of said power converter to a third predetermined battery voltage when a charging process is terminated.

11. The battery charging circuit of claim 1 , wherein said second signal further indicates a charging termination of said battery pack.

12. A battery charging circuit comprising:

a power converter operable for providing a charging power to a battery pack; and

a charging controller coupled to said power converter and said battery pack and operable for generating a first signal for controlling an output of said power converter, wherein said charging controller comprises:

a first error amplifier operable for comparing a charging current of said battery pack to a predetermined charging current;

a second error amplifier operable for comparing an output of said power converter to a first predetermined battery voltage; and

a multiplier operable for multiplying a second signal representative of a cell number of said battery pack by a third signal representative of a predetermined maximum cell voltage of said battery pack,

wherein said first predetermined battery voltage is equal to a portion of the product of said second signal and said third signal,

wherein said first signal is generated according to an output of said first error amplifier when a battery voltage of said battery pack is less than said first predetermined battery voltage, and wherein said first signal is generated according to an output of said second error amplifier when said battery voltage reaches said first predetermined battery voltage.

13. The battery charging circuit of claim 12 , further comprises a charging control switch coupled between said power converter and said battery pack and operable for receiving a switch control signal from said charging controller for transferring said charging power to said battery pack, wherein said battery pack is charged in a mode selected from at least a continuous charging mode and a pulse charging mode according to said switch control signal.

14. The battery charging circuit of claim 13 , wherein said switch control signal comprises said first signal when said battery voltage is less than a predetermined minimum battery voltage.

15. The battery charging circuit of claim 13 , wherein said switch control signal comprises a fourth signal when said battery voltage is greater than a predetermined minimum battery voltage, and wherein said fourth signal comprises a pulse signal.

16. The battery charging circuit of claim 13 , wherein said first signal controls said output of said power converter to a second predetermined battery voltage when said battery pack is charged in said continuous charging mode.

17. The battery charging circuit of claim 13 , wherein said pulse charging mode comprises a constant current phase and a constant voltage phase, and wherein said first signal controls said output of said power converter to said first predetermined battery voltage when said battery pack is charged in said constant voltage mode.

18. The battery charging circuit of claim 12 , wherein said first signal controls said output of said power converter to a second predetermined battery voltage when a charging process is terminated.

19. The battery charging circuit of claim 12 , wherein said first predetermined battery voltage comprises a predetermined maximum battery voltage.

20. The battery charging circuit of claim 12 , wherein said predetermined charging current comprises a predetermined pre-conditioning charging current when said battery voltage is less than a predetermined minimum battery voltage.

21. The battery charging circuit of claim 12 , wherein said predetermined charging current comprises a predetermined maximum charging current when said battery voltage is greater than a predetermined minimum battery voltage and less than said first predetermined battery voltage.

22. A method for charging a battery pack, comprising:

transferring a charging power from a power converter to said battery pack through a charging control switch in a continuous charging mode and a pulse charging mode;

generating a first control signal to control an output of said power converter;

selectively controlling said charging control switch by said first control signal and a second control signal according to a comparison of a battery voltage of said battery pack with a predetermined minimum battery voltage;

generating said first control signal according to an output of a first error amplifier when said battery voltage is less than a predetermined maximum battery voltage;

generating said first control signal according to an output of a second error amplifier when said battery voltage reaches said predetermined maximum battery voltage; and

multiplying a third signal representative of a cell number of said battery pack by a fourth signal representative of a predetermined maximum cell voltage of said battery pack,

wherein said predetermined maximum battery voltage is equal to a portion of the product of said third signal and said fourth signal.

23. The method of claim 22 , further comprising:

selecting said first control signal when said battery voltage is less than said predetermined minimum battery voltage; and

charging said battery pack in said continuous charging mode.

24. The method of claim 22 , further comprising:

selecting said second control signal when said battery voltage is greater than said predetermined minimum battery voltage; and

charging said battery pack in said pulse charging mode.

25. The method of claim 24 , further comprising:

charging said battery pack in a constant current mode when said battery voltage is less than said predetermined maximum battery voltage.

26. The method of claim 24 , further comprising:

charging said battery pack in a constant voltage mode when said battery voltage reaches said predetermined maximum battery voltage.

27. The method of claim 22 , further comprising:

sensing a charging current of said battery pack by said first error amplifier; and

comparing said charging current with a predetermined pre-conditioning charging current when said battery voltage is less than said predetermined minimum battery voltage.

28. The method of claim 22 , further comprising:

sensing a charging current of said battery pack by said first error amplifier; and

comparing said charging current with a predetermined maximum charging current when said battery voltage is greater than said predetermined minimum battery voltage and less than said predetermined maximum battery voltage.

29. The method of claim 22 , further comprising:

sensing said output of said power convert by said second error amplifier; and

comparing said output of said power converter with said predetermined maximum battery voltage when said battery voltage reaches said predetermined maximum battery voltage.

30. The method of claim 22 , further comprising:

controlling said output of said power converter to a first predetermined battery voltage when said battery pack is charged in said continuous charging mode.

31. The method of claim 22 , further comprising:

controlling said output of said power converter to said predetermined maximum battery voltage when said battery voltage reaches said predetermined maximum battery voltage.